EFFECT OF THE ENAMEL CONDITIONERS ON INITIAL SHEAR BOND STRENGTH OF RESIN-MODIFIED GLASS IONOMER ADHESIVE TO ENAMEL

Objective: To study the effect of different enamel conditioners on initial shear bond strength of resin-modified glass ionomer adhesive to enamel. Materials and methods: Fifty-five human premolars were divided into 5 groups (11 samples for each group). Group 1 was the controlled group without conditioner. Group 2-4 were experimental groups which were conditioned with 20% polyacrylic acid, 37% phosphoric acid and self-etching primer, respectively. For group 1-4, the brackets were bonded with resin-modified glass ionomer adhesive (Fuji ortho LC). Group 5 was the Benchmark group which was conditioned with 37% phosphoric acid and the brackets were bonded with composite resin adhesive (Transbond XT). After light activation for 5 minutes, the shear bond strengths of 10 specimens from each group were tested by universal testing machine. The forces that debonded the brackets from enamel surface were recorded. The mean of shear bond strength among groups were compared by one-way ANOVA. The adhesive remnant indices (ARI) in each group were measured and tested by the Chi-square at 95% confidence interval. One remaining specimen from each group was used to investigate of resin penetration pattern into enamel under scanning electron microscope. Results: Mean and standard deviations of shear bond strengths of group 1, 2, 3, 4 and 5 were 8.4 ± 2.0, 10.8 ± 0.7, 14.6 ± 3.0, 13.7 ± 1.7 and 21.5 ± 4.0 megapascal, respectively. There is no significant difference between group 3 and 4 (p=0.328). Types of enamel conditioners were statistically significant to ARI scores (p<0.05). SEM image revealed that the size and number of resin tags in self-etching primer group are greater than the other experimental groups. Conclusion: The use of phosphoric acid or self-etching primer as a conditioner can increase initial shear bond strength of resin-modified glass ionomer adhesive